Breakerless flywheel magneto ignition system



Oct. 8, 1968 3,405,347

BREAKERLESS FLYWHEEL MAGNETO IGNITION SYSTEM T. SWIFT E AL 5Sheets-Sheet 1 Filed Sept. 30, 1965 O E WYD 1. E0 1 I! v NE M 6 0M 4 6 Z4 l| l 6 MNC M 7 m L. Y p p .ln. \0 0 ram 0 a i 2 E wa O. .0 O 6 4 3 5 85 7 f 2 R 9 .M k a E! 1 V '1 :i t 3 im! !!w! 1 0 Q I t -KA M I i l ll! ll l I I I l I I l I I l i l l I I tlrullllli r. l a i 3 o 4 I w W M m &m Z .w m Mn me I m c MEGA/6T0 l I Oct. 8, 1968 T. E. SWIFT ETBREAKERLESS FLYWHEEL MAGNETO IGNITION SYSTEM Filed Sept. 30; 1965 5Sheets-Sheet 2 /ZZ i w Peumer .mae

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BREAKERLESS FLYWHEEL MAGNETO IGNITION SYSTEM Filed Sept. 30, 1965 5Sheets-Sheet 4 l "Mun,

m flymaigi idm THOMAS 0 W/N 5 W/F 7 5L Wl/V JOHN BEAYLE' Y Q! myCAMPBELL NODD/N [75 QMM MIJ M 8 United States Patent O 3,405,347BREAKERLESS FLYWHEEL MAGNETO IGNITION SYSTEM Thomas Edwin Swift, WestSpringfield, Elwin John Brayley, East Longmeadow, and Ray CampbellNoddin, Chicopee, Mass.; said Swift and said Brayley assignors, by mesneassignments, to Eltra Corporation, Toledo, Ohio, a corporation of NewYork Continuation-impart of application Ser. No. 469,076,

July 2, 1965. This application Sept. 30, 1965, Ser.

15 Claims. (Cl. 322-91) ABSTRACT OF THE DISCLOSURE This inventionprovides an improved magneto system which is reliable and stableirrespective of environmental conditions, wear and the like, and has nocontacts, breakers or other moving parts in addition to the rotoritself. The conduction in the magneto winding means is initiated andterminated by a solid state device and preferably a solid statethreshold device which is responsive to impulses of electrical energy tochange its state between one of conduction and nonconduction wherebymagneto operation can be controlled by relatively short duration triggerimpulses. The trigger impulses may automatically produce a spark advancefor increased magneto speeds.

This invention relates to improved magneto systems, and, moreparticularly, to an improved magneto system utilizing solid statecontrol devices for control purposes and rotary devices for voltagegeneration.

This application is a continuation-in-part of our earlier application,Ser. No. 469,076, filed July 2, 1965, and now abandoned.

Magneto systems are widely used throughout industry for variouspurposes, but their greatest use is in ignition systems for automotivevehicles, marine engines, aircraft engines, engines for portableequipment, auxiliary power units and the like.

Various techniques have been employed to utilize rotating magneticfields to generate substantial impulse voltages for ignition purposes.One successful flywheel magneto system is that disclosed in BrownleePatent No. 2,583,466. As disclosed in that patent, the magneto systemincludes a fixed electromagnetic structure comprising first and secondcoils wound upon the central leg of an E-type core structure. The coreis mounted on a stator member and the faces of the three legs of thecore are shaped to conform to an outer annular surface of the stator.This surface conforms to the inner surface of a rotor and flywheel. Thecore faces cooperation with an armature rotatably mounted in the rotorand flywheel and a permanent magnet is included in the armaturestructure. As the flywheel turns, it generates a cyclic flux in the E-shaped core. The flux in the central leg is first of one given polarityand then rapidly reverses to the opposite polarity. The rapid fluxreversal is generally employed in some manner to generate an ignitionimpulse in the second coil.

In the flywheel magneto of the instant invention, the substantialvoltage for spark ignition is generated in the second coil bymaintaining conduction in the first coil until a time when the fluxreversal, dqb/dt, is near its maximum value and then rapidly opening thecircuit of the first coil to generate a very substantial transientvoltage in both coils. As is well understood in the art, a low impedanceclosely coupled coil in a magnetic circuit experiences an inducedcurrent which opposes any change in flux in that magnetic circuit and,thus, the flux density in the core during a magneto cycle when the firstcoil is 3,405,347 Patented Oct. 8, 1968 effectively shorted will be lessthan the flux value when the first coil is open or in a high impedancecircuit. Thus, when the circuit of the first coil is opened, theinherent operation of the circuit will tend to produce a step-functionflux increase which will, in turn, induce very substantial voltages inthe first and second coils. The substantially increased voltage in thesecond coil will be sufficient for breakdown of the spark gap andignition.

In accordance with the instant invention, systems are provided includingsolid state control devices and trigger windings to effectivelyshort-circuit the first coil at predetermined times in each magnetocycle and to rapidly alter the parameters of the circuit of the firstcoil at a critical time to produce an open-circuit effect to generate anignition impulse. The solid state control devices are controlled in partby a triggering assembly including coil means and an associated armaturemounted for timed relative rotation.

It is one principal object of this invention to provide an improvedmagneto system which is reliable and stable irrespective ofenvironmental conditions, wear and the like.

It is another important object of this invention to provide an improvedmagneto system which relies for its operation upon the electromagnetictriggering of semiconductor devices for control of the operationthereof.

A further object of this invention is the provision of an improvedmagneto system having a magneto coil as sembly and a triggering coilassembly mounted in cooperation with a rotatable flywheel havingappropriate armatures mounted thereon for magneto operation.

Another object of this invention is the provision of an improved magnetosystem including triggering means requiring no mechanical contacts,camming surfaces or tub bing or contacting parts of any kind.

A further object of this invention is the provision of a magneto systemusing solid state control devices and means for automatically varyingignition timing with engine speed by controlling the triggering of saiddevices.

It is another object of this invention to produce a magneto systemutilizing solid state threshold devices to provide improved output waveform, more consistent firing time, and inherent spark retardation.

Further and additional objects of this invention will become manifestfrom a consideration of this description, the accompanying drawings andthe appended claims.

In one form of this invention, an engine mounted stator and an enginedriven rotor are provided. The stator has an E-shaped magneto core withtwo windings mounted on the central leg and a triggering core having apermanent magnet disposed therein and one or more triggering coilsdisposed thereon. A triggering armature and a magneto armature andmagnet are mounted in a flywheel rotatably mounted on the stator andshaped to cooperate with the magneto core and the triggering core toproduce closely coupled magnetic field stmctures during some portion ofeach cycle of rotation thereof. A solid state control device iscontrolled by the triggering coil means and, in turn, controls thecurrent flow through one of the magneto coils to produce a step functionflux change. As is well known, such a flux change induces voltages inassociated coils in accordance with the equation is. -a

The second magneto coil is closely coupled to the first coil, has a verysubstantial number of turns, and experiences a very high inducedvoltage. This voltage provides the impulse output for ignition purposesand may be connected directly to a spark plug, or to a distributorwhich, in turn, energizes a plurality of spark plugs.

For a more complete understanding of this invention,

reference will now be made to the accompanying drawings wherein:

FIGURE 1 is a diagrammatic view of the mechanical elements of oneembodiment of this invention;

FIG. 2 is a series of curves representing the electrical and magneticphenomena occurring in the embodiment of FIG. 1 during the ignitioncycle thereof;

FIG. 3 is a circuit diagram of the embodiment of FIG. 1;

FIG. 4 illustrates an alternate embodiment of the invention including analternate means for mounting the various components;

FIG. 5 is an alternate circuit diagram of the various em bodiments ofFIGS. 1, 4 and 6;

FIG. 6 illustrates another embodiment of the invention providing analternate manner in which the various com ponents may be mounted in thestator and rotor;

FIG. 7 is a circuit diagram illustrating a third embodiment of thisinvention employing three triggering coils;

FIG. 8 is a set of curves illustrating the electrical and magneticphenomena occurring in the embodiment of FIG. 7 during the typicalignition cycle;

FIGS. 9-14 illustrate the relative disposition of the stator and rotorin the embodiment of FIG. 1 during a typical ignition cycle;

FIG. 15 is a circuit diagram illustrating a fourth embodiment of theinvention; and

FIG. 16 is a set of curves illustrating the electrical and magneticphenomena occurring in the embodiment of FIG. 15 during the typicalignition cycle.

Referring now to the drawings, FIGS. 1, 4 and 6 illustrate threemechanical arrangements of the basic elements of the invention, namely,the magneto coil system, the triggering coil system, and the controlcircuitry. On the other hand, FIGS. 3, 5, 7 and 15 illustrate fourcircuit arrangements utilizing one, two, three and two triggering coils,respectively. While all four embodiments incorporate certain basicconcepts of this invention, each has its special advantages, and eachmay be employed in any one of the three mechanical arrangements.

Mechanical construction of magneto system Referring more particularly toFIG. 1, a flywheel or rotor 20 is illustrated diagrammatically mountedon a stator 60. As the bearings for the rotor 20, the configuration ofthe stator 60', and the mechanical construction of the parts for balanceand the like have no hearing whatsoever upon the invention, all detailsthereof have been omitted. The basic arrangement shown in FIGS. 1 and 2of the Brownlee Patent No. 2,583,466 may be used for example, with themodifications illustrated herein.

The flywheel 20 is mounted to rotate in the direction illustrated byarrow 22. It is formed of a nonmagnetic material and includes therein apair of magnetic magneto pole pieces 24 and 26 which cooperate with amagneto coil assembly and a pair of magnetic trigger pole pieces 28 and30 which cooperate with a triggering coil assembly. A permanent magnet32, preferably formed of alnico or some similar high permeability, highretentivity material, is disposed between the pole pieces 24 and 26 andbetween the pole pieces 28 and 30. The particular polarity of the magnetis not critical because in this embodiment the magneto and triggeringcircuits will be properly phased because of the use of a single magnet.The pole parts 24, 26, 28, 30 and 32, and counterweights as required,may be cast into a unitary flywheel formed of aluminum or the like.

The magnetic core 34 of the magneto coil assembly 33 is mounted adjacentthe flywheel 20 on the stator 60 and includes a central leg 36, aforward leg 38, and a final leg 40. First and second coils or windings42 and 44 are wound upon the central leg 36 and are connected throughappropriate conductors 46 to a component housing 48. The componentscontained in housing 48 are for the control circuits to be describedhereinafter and are conventional and readily available electroniccomponents. Thus they are not individually illustrated in FIG. 1, butare all included within the circuit diagrams forming a part of thisdisclosure.

A trigger coil assembly 51 is mounted upon the stator 60 and includesone or more triggering coils 50 mounted on a triggering core 52. Thecore 52 includes forward leg 56 and final leg 54 which cooperate withthe poles 28 and 30 mounted in fiyweel 20 to produce desired fluxlinkage. The opposed faces of the various armatures and cores are shapedto fit closely for maximum magnetic coupling but are free of mechanicalcontact. The core 34 may be fixed'to the stator 60 which is adjustablymounted on the associated engine for timing adjustment. The core 52 issecured to a mounting plate 58 which is secured on the stator 60 by apair of machine screws 62 and 64. The machine screws 62 and 64 arethreaded into the stator 60 through slots 66 formed in the mountingpiece 58, and the slots are slightly arcuate so that the triggerassembly can be adjusted relative to the magneto core 34 to provideadjustment of the so-called edge gap (the angular relationship betweenthe magneto core 34 and the trigger core 52). The trigger coil 50 isconnected to the component housing 48 through conductor 68.

As will be more apparent from the description of the circuit and itsoperation, rotation of the flywheel 20 in the direction indicated byarrow 22 will result in the generation of useful magnetic flux in thecenter leg 32 of magneto core 34 by successively coupling the armaturepol-es 26 and 24 to the central leg 36 and forward leg 38 of the magnetocore 34 and then the final leg 40 and central leg 36. As the flywheelproceeds in the direction indicated, the direction of flux produced bypermanent magnet 32 in central leg 36 will be rapidly reversed and issubstantially zero as the flywheel passes through the positionillustrated in FIG. 1. This is illustrated by curve 98 at time T in FIG.2. The permanent magnet 32 will also induce a flux in trigger core 52 asthe armature poles 28 and 30 pass adjacent to the core legs 56 and 54,respectively. The flux generated in trigger core 52 is substantially atits maximum value at theposition of FIG. 1 as illustrated by curve 99 inFIG. 2, utilized to generate control currents for the magneto as will bedescribed.

The operation of the circuit of FIG. 3

Referring now to FIG. 3, the first winding 42 of the magneto assembly isdiagrammatically shown, coupled magnetically to the second Winding 44.The magnetic coupling and source of magnetic flux provided by core 34and the permanent magnet 32 are illustrated by arrow 70. The secondwinding 44 is connected between the ground bus 72 and the rotor 74 of adistributor. Each of the points of the distributor 76 will be connectedto the central electrode of aspark plug, although only one spark plug 78is illustrated diagrammatically. The side electrode 80 of the spark plugis connected to ground. Thus a voltage impulse in second coil 44 will beapplied through distributor 76 to the spark plug 78, and if sufiicient,will provide engine ignition.

Connected directly across the first coil 42 are a capacitor 82, a diode84 and a solid state threshold device 86. The term solid state thresholddevice or merely threshold device means any one of a plurality of solidstate devices which are presently available and others which may becomeavailable for controlling the flow of current between an anode terminaland a cathode terminal or socalled conductive terminals by virtue of atriggering signal applied to a so-callod gate or control terminal. Suchdevices are identified in various ways by the manufacturers who makethem available, and the term solid state threshold device is intended toencompass all such devices. While most of the devices satisfying thisdefinition are four layer, three terminal devices, other four and fivelayer devices may also be adapted to the invention.

Typical devices satisfying this definition are the PNPN silicongate-controlled switches (GCS) sold by Texas Instruments Incorporatedunder the designation types TICll, 12, 13 and 15, so-called TOTCR types241UA- UM sold by Westinghouse Electric Corporation, and socalledTranswitches sold by Transitron Electronic Sales Corporation. Thedevices are all characterized in that they present a relatively highimpedance to the flow of current between their conductive terminals(anode to cathode) until they are properly triggered by the applicationof current to the control terminal (gate). Thereafter, the impedancebetween the conductive terminals becomes the very low and there is nosignificant linear control of the current flow by the application ofsignals to the control terminal. However, upon the application of asubstantial reverse current to the control terminal, it is possible torender the device nonconductive and it held nonconduclive for a periodin the order of 100 microseconds, the device will remain nonconductiveeven after the control signal is removed.

One typical example of the operating characteristics of such a device isthat of Transitrons Transwitch. In that device, the maximum forward andreverse currents at normal temperatures are about microamperes. To turnthe device on requires a positive signal of approximately 1 volt at thecontrol terminal and a current of 15 milliamperes. Once the device isconductive, the control terminal is ineffective at the 1 volt level, theforward voltage across the device drops to about 2 volts, and the deviceis capable of conducting up to 5 amperes. To reverse the thresholdphenomena and render the device nonconductive, a signal of oppositepolarity must be applied to the control terminal. This signal must be upto volt and provide a current up to 200 milliamperes. While such acontrol signal will stop current flow between the conductive terminalswithin a few microseconds, some control current must be maintained forapproximately 100 microseconds to assure return of the quiescent or offcondition. Thus, the energy required to turn the device oil issubstantially greater than the energy required to turn the device on.

Sequence of operations Returning now to the circuit of FIG. 3, thecontrol terminal 88 of the threshold device 86 is energized throughresistor 90 from the trigger coil 50. The arrow 92 represents themagnetic structure associated with coil 50 including the core 52 and thepermanent magnet 32 with its associated armature legs 28 and30. Theinterrelationship of the magnet coil assembly, trigger coil assembly andcircuit components is such that the diode 84 effectively shorts coil 42during initial flux build-up, threshold device 86 shorts winding 42during flux reversal, and device 86 then opens the winding 42 to providea voltage impulse.

The operation of the foregoing circuit can be best understood byreferring to FIG. 2. The abscissa in FIG. 2 is time and represents onlya small portion of one complete revolution of the flywheel in the orderof 45 Specific times are designated on the chart of FIG. 2 as T throughT and the relative positions of the coils and armature for the first sixof these positions are illustrated in FIGS. 9-14. As the armature poles26 and 24 approach the core legs 36 and 38 shown in FIG. 9 at time T theleading pole 26 begins to cover the central leg 36 of core 34, and thetrailing pole 24 begins to cover the forward leg 38. This induces a fluxfrom magnet 32 in the central leg 36 as illustrated by the top curve 98of FIG. 2. At time T the flux begins to increase relatively gradually.At time T the armature poles 26 and 24 are somewhat more than halfcovering the associated core legs 36 and 38 as shown in FIG. 10. At thistime, T the flux is changing at its maximum rate dqb/dt.

The relationship at time T is illustrated in FIG. 11 where the armaturepoles 26 and 24 are substantially completely covering the core legs 36and 38. Thus, at time T the rate of change of flux d/dt is substantiallyzero, and the flux curve 98 is at a maximum. As the flywheel continuesto the position shown in FIG. 12 (representing T the armature poles 26and 25 are moving beyond the core legs 36 and 38, and the flux densityin the central leg 36 is diminished. The relationship at time T isillustrated in FIG. 13, showing the armature poles 26 and 24 balancedbetween the central leg 36 and the forward leg 38 and last leg 40. Thus,while there is substantially opposed flux in the outer legs 38 and 40,the net flux in central leg 36 is substantially zero, and the rate ofchange do/dt is at a steep negative maximum as shown by curve 98 in FIG.8. As the flywheel continues, as shown in FIG. 14, the leading pole 26begins to cover the last leg 40, and trailing pole 24 begins to covercentral leg 36 producing a substantial flux change at T as illustratedin FIG. 2. This flux pattern generates induced voltages in both thefirst and second windings 42 and 44 which under open circuit conditionsdescribe the curve 101 in FIG. 2.

At the same time that the foregoing sequence is occurring in the magnetowinding structure, the trigger winding structure 52 is experiencing arelated flux phenomenon. As the flywheel 20 carries the trigger poles 30and 28 toward the respective core legs 54 and 56, a positive-going fluxis induced in coil 50. The pattern of flux generated in coil 50 isillustrated by curve 99 in FIG. 2, and the current generated thereby isillustrated as curve 103. The flux rises to a significant value at timeT has a zero rate of change at T exhibits a steep slope at T and issubstantially zero at T Because of this flux pattern, significantforward current at T and substantial reverse current at time T areprovided.

Relating these various flux and current phenomena to the circuit shownin FIG. 3 will make the operation of that circuit clear. As the magnetoarmature approaches the core, increasing positive flux in first winding42 induces a negative voltage in the first winding in accordance withthe relationship: E=-Nd/dt. If the windings are open, the shape of thecurve would be as illustrated by the first negative hump 101a in FIG. 2.However, diode 84 is connected directly across first winding 42 andprovides a shunt whereby substantial current is flowing through diode 84at time T maintaining the voltage thereacross at a relatively low value.This shunting of the first winding 42 also prevents the build-up ofvoltage in second winding 44, and also avoids the possibility of amaverick spark during the early portion of the ignition cycle. Thecurrent reverses by virtue of the change in magnetic flux, and the diode84 is nonconductive, the capacitor 82 is charged and the thresholddevice 86 is in a blocking state. Thus, the voltage across winding 42builds up as shown by curve 101b in FIG. 2. A typical current in firstwinding 42 is illustrated by curve 105 in FIG. 2.

At time T the voltage from trigger coil 50 applied to the controlterminal 88 of threshold device 86 also builds up by virtue of the fluxin the coil 50. This voltage produces control current in accordance withcurve 103, and this control current renders the threshold device 86conductive between its main conductive terminals, anode 94 and cathode96. Thus, the first winding 42 is again effectively shorted, now forcur-rent in the positive direction, reducing the flux build-up in thecore 34.

At time T the voltage induced in trigger coil 50 has reversed, as shownin FIG. 2, and is passing negative current through resistor and thecontrol terminal 88 of suflicient magnitude to render the thresholddevice 86 nonconductive. In accordance with well-known magnetofundamentals, a step-function cut-off of the device 86 tends to producea drastic change in flux in the core 34 as diagrammatically illustratedby curve 98a in FIG. 2. The rapid flux change in the core induces anignition voltage in second winding 44 which is applied throughdistributor 74 to the spark plugs 78. The secondary voltage isillustrated as curve 100 in FIG. 2 and, as shown in the curve, a suddenimpulse of voltage is applied to the spark gap at time T resulting inspark breakdown. Upon spark breakdown, the second winding 44 iseffectively shorted, passing a very substantial secondary current asillustrated by curve 102, and the voltage thereacross drops drastically.A damped harmonic signal can be observed because of the inertia of thevarious circuit components and particularly winding 42 and capacitor 82.This arrangement improves the load line of the circuit and reduces themagnitude of the transients therein. Socalled maverick impulses andignition impulses at an improper time between T and T and after T areavoided by diode 84.

The trigger coil current wave shape 103 is timed with respect to themagneto current by determining the angular segment represented by thetime lapse between T and T based upon the primary voltage curve 101.This measurement establishes the width of the armature poles 28 and 30and the core legs 54 and 56. The rise of current wave form 103 is thenadjusted for proper timed energization of the control terminal 88.

The two trigger impulse embodiment 07 FIG. 5

An alternate embodiment of the invention having a very similar circuitarrangement and physical structure, but having significant advantages,is illustrated in FIG. 5. As shown in FIG. 5, two triggering coils areemployed. The first winding 42 and second winding 44 are mounted on themagnetic structure as in the embodiment of FIG. 3, diagrammaticallyillustrated by arrow 70. Second winding 44 is connected from groundthrough a distributor 76 to the gap of a spark plug 78 and, in turn, toground. A

capacitor 82 for energy storage and improved load line characteristicsis connected across first winding 42, and diode 84 is also connectedacross coil 42 to shunt the negative pulse induced in winding 42. Thethreshold device 86 is connected across the winding 42 with its controlterminal 88 connected through a resistor 90 to the first trigger coil50. A second trigger coil 104 is wound upon the same core 52 as the coiland is connected to the control terminal 88 of the threshold device 86through a resistor 106. If required for timing purposes, a capacitor 108may also be employed in a manner to be described for impedanceadjustment and phasing.

The circuit illustrated in FIG. 5 provides improved control overignition timing with varying engine speed. As described above, it isfundamental in magneto operation that induced voltages, which are afunction dqb/dt, vary with rotation speed. This basic characteristic ofmagneto systems is utilized in the instant invention to provide timingadvance at accelerated speeds. The operation of trigger coil 50 and anexplanation of the current curve 103 1 appear above. This operation isalso characteristic of the embodiment of FIG. 5 at low engine speeds.However, the second trigger coil 104 has a substantially lowerinductance and a larger series resistance whereby the pulse resultingtherefrom leads the current in coil 50 at normal engine speeds as shownby curve 107 in FIG. 2. The lead increases with increased engine speeds.Furthermore, the circuit components are selected so that the combinedenergy of coils 50 and 104 is required to control device 86. However,with increased speeds, the voltage rises and current in coil 104 assumesgreater and earlier control. In this embodiment, both timing, so-ca'llededge gap, and the spark advance can be adjusted by varying resistors 90and 106, or the use of capacitor 108. In one typical embodiment of theinvention, resistor 90 is 18 ohms, resistor 106 is 68 ohms, coil 50 hasan inductance of mh. and a resistance of 44 ohms, and coil 104 has aninductance of 14 mh. and 18 ohms. In all other respects, the circuit ofFIG. 5 functions in a manner substantially identical to the circuit ofFIG. 3.

8 The three winding embodiment of FIG. 7

Still another embodiment of the invention is illustrated in FIG. 7, andthe electrical and mechanical operation thereof is illustrated in thecurves of FIG. 8. In the embodiment of FIG. 7, three triggering coils50, 104 and 162 are employed. The circuit works upon the same principleas already described with the second winding 44 connected throughdistributor 76 to the spark plug 78 and the first winding 42 shunted bycapacitor 82, diode 84 and threshold device 86. The three coils 50, 104and 162 are all wound upon the same trigger core structure and, thus,the voltages generated therein are as shown in FIG. 8.

In FIG. 8, the curve 161 represents the current in coil 50, and curve163- represents the current in coils 104 and 162.

Triggering coil 50 directly connected to control terminal 88 initiatesconduction through threshold device 86 at an early point in the cycle,substantially at time T The voltage induced in coil 162 chargescapacitor 164 through diode 166 such that capacitor 164 has the chargeas in dicated in FIG. 7. The energy stored in capacitor .164 is utilizedto turn 011 the threshold device 86 more rapidly and positively thanwould be possible in the circuits described above with respect to FIGS.3 and 5. Furthermore, the circuit can handle greater power requirements.

As the trigger magnet passes the central position and voltages in thetrigger coils 50, 104 and 162 are reversed, discharge of capacitor 164is blocked by diode 166 and the positive voltage of curve 163 is appliedto a control terminal 168 of a gate controlled rectifier or so-calledSCR 170. At time T the signal from trigger coil 104 renders SCR 170conductive and discharges capacitor 164 through resistor 172 and thecontrol terminal 88 of threshold device 86. Resistor 174 is provided forprotection of the threshold device 86. In the embodiment of FIG. 7,trigger coil 162 provides a source of energy for capacitor 164, and thisenergy is dumped into threshold device 86 at the critical time T throughSCR 170 in order to terminate conduction at a rapid and positive rate inthreshold device 86. This step function of current through first coil 42produces a substantial transient voltage in second coil 44 sufficient toinitiate spark ignition.

The two trigger impulse embodiment of FIG. 15

The embodiment of FIG. 15 is very similar to the embodiment of FIG. 5 inits general configuration and overall operation. However, it hasimportant relative advantages and disadvantages, as will. be describedbelow. In this embodiment the control device is an NPN switching typetransistor .176. In employing the transistor 176 as the solid statecontrol device in the various configurations already described, the polepieces, such as pole pieces 28 and 30 of FIG. 1, must be altered to varythe shape and length of the pulse generated thereby. In the embodimentof FIG. 15, two coils 178 and 1-80 are wound upon a trigger core such asthe core 52 in FIG. 1. The coils and core are so designed and relatedthat trigger flux, as illustrated by curve 214 in FIG. 16, is generatedproducing the currents shown by curves 202 and 204.

The coils 178 and 180 are connected in common to a ground bus 182 andthrough respective resistors 184 and 186 to the base of transistor 17 6.Transistor 176 acts as a three terminal switch in the embodiment of FIG.15 and the switching signals are applied to the base of transistor 176from windings 178 and 180. The switched energy is generated in firstWinding 188 and applied to the parallel combination of diode 190,transistor 1'76 and capacitor 192.

As the flywheel rotates and the pole pieces approach the magneto windingassembly, a flux is generated in the magneto Winding 188 which producesan initial current substantial-1y by-passed by diode 190. Thereafter apositive voltage is generated which is utilized by transistor 176 togenerate the spark impulse. The characteristics of the circuit areillustrated in FIG. 16 where it can be seen that the positive build-upof flux between the time T and the time T as shown by curve 194,produces a small negative going voltage 196. From time T to time T theflux diminishes to zero as the flux in the two outer core legs isbalanced. At time T the voltage has risen to a positive maximum as shownby curve 196.

During the positive voltage cycle the diode 190 is biased off so that asubstantial voltage appears between the collector and the emitter oftransistor 176. The voltage build-up in the first winding is clear fromcurve 196 and the voltage in the second winding 198 is illustrated bycurve 200 in FIG. 16.

The triggering voltage generated in winding 178 is shown in curve 202and the voltage generated in winding 180 is illustrated by curve 203 inFIG. 16, where it can be seen that all control is provided by the first,positive going half cycle which has been substantially lengthened incomparison to the previous embodiments. By vi;tue of the inductance ofthe windings and the related resistors 184 and 186, the two windings 178and 180 which are wound on a common triggering core such as core 52 inFIG. 1 experience similar voltage excursions at a slightly displacedtime. Thus, the current in winding 180 leads the current in winding 178by a small angle and both currents are applied to the base of transistor176 in an additive positive going direction to produce base currentthrough conductors 204 and 206 to ground.

The base current biases the transistor 176 for conduction so that fromtime T to time T the bias currents through the transistor 176 exceed thelevels indicated by broken lines 216 and the transistor is, therefore,switched on and conductive. At time T the current through transistor 176has been reduced to a point where transistor 176 is cut oil, producing arapid, negative flux change in the primary winding 188 as illustrated bypeak 288 in FIG. 16. This substantial negative going pulse 208 producesvoltage breakdown across the spark gap 211) and, consequently, anignition current impulse at time T as illustrated by curve 212. Thecapacitor 192 provides additional energy to the primary winding 188which is reflected as increased current across the spark gap 210, asillustrated by the curve 212.

Thereafter, the primary voltage falls until, at time T the flux reachesa negative maximum and the subsequent negative voltage impulse isshunted through the diode 190 until a new cycle starts at time T In thisembodiment, as in the embodiment of FIG. 5, there is a natural andautomatic phase shift or ignition retard produced by the use of twotrigger windings connected in parallel through resistors, the circuit ofwinding 180 having less inductance and greater resistance than thecircuit of winding 178. As the engine is accelerated the rate of changeof flux increases providing greater relative control in winding 180 and-producing ignition at an earlier time and, consequently, a sparkadvance.

While an NPN transistor has been described in the embodiment describedabove, it will be apparent that a PNP type may be employed with equalsatisfaction. However, in that event the polarity of the diode 190 willbe correlated to the transistor and the windings 178, 180 and 188 willbe reconnected to provide an initial negative impulse for controlpurposes. Moreover, while a common emitter configuration is hereemployed, with proper design a common base configuration could also beemployed. The transistor version of the invention as shown in FIG. 15has certain advantages over the embodiments described above which employthreshold devices. In general, the embodiment of FIG. 15 will be lesscostly and have a lower saturation voltage and, thus, slightly greaterefliciency. However, the embodiments of FIGS. 3, 5 and 7, which usethreshold devices, have the advantages of greater precision in timing, agreater control of the timing, the ability to handle larger power in themain gap and the ability to employ multiple pulses for independentcontrol of the turn-on and turn-01f times.

The transistor of FIG. 15 and the threshold devices as defined in FIGS.3, 5 and 7 comprise solid state control devices. Solid state controldevices is used in this specification to describe any solid state deviceor a combination of elements including a solid state device which arecapable of producing the effects described with respect to theembodiments of FIGS. 3, 5, 7 and 15. Namely, any solid state device orassembly which bypasses the current from the primary winding during aninitial portion of the positive-going cycle and thereafter effectivelyopens the primary circuit in a very short time to produce a substantialflux excursion and consequent ignition impulse is a solid state controldevice.

In addition to the foregoing specific examples of solid state controldevices, an SCR might be employed in a similar circuit in cooperationwith a capacitor or other storage system for effectively opening the SCRfor a sufiicient time to turn off the SCR so that a desired voltageimpulse is produced.

Alternate mechanical constructions While one particular layout of themechanical components is illustrated in FIG. 1, the components may berearranged for greater compactness and an increased flywheel size. Onesuch alternate construction is illustrated in FIG. 4. There an enlargedflywheel carries the magneto armature 122 and associated permanentmagnet 124. Also, carried on magneto flywheel 120 is the diametricallyopposed trigger armature 126. However, in this embodiment, the triggerarmature 126 does not include a permanent magnet, and both the magnetocoil construction and triggering coil construction are disposed withinthe flywheel. A magneto core 128 is disposed within the flywheel andmounted on a stator 130. The core 128 has legs 132, 134 and 136 shapedto conform to the internal surfaces of the flywheel, but otherwise thestructure is the same as that described with respect to FIG. 1. Thefirst and second windings 42 and 44 are disposed on the central leg 136in the manner already described, and the windings are connected througha cable 46 to the control circuit 48.

A permanent magnet 138 is necessary in the magnetic trigger circuit, asthe magnet 124 cannot perform the dual function of magnet 32 in FIG. 1.Poles 140 and 142 are secured to the magnet 138, and the assembly ismounted on a plate 144 which is, in turn, adjustably mounted by screws146 and elongate openings for adjustment on stator 130. One or morecoils are formed upon the legs 140 and 142, and these may include coil50, coil 104 and coil 162.

If it is desirable to mount the magnet associated with the triggeringcoil in the flywheel, the embodiment diagrammatically illustrated inFIG. 6 is advantageous. Therein, the magneto core 128 and windings 42and 44 are as described in FIG. 4. The magneto magnet 150 and poles 152and 154 are shown diagrammatically, but function as already describedwith respect to FIG. 4. The trigger coil 50 and additional coils asdesired are mounted on a core 156 to cooperate with armature poles 158and 159 and permanent magnet 160 mounted in the flywheel. In such aconstruction, the critical factor is to select the gaps between thepoles 158 and 159 of the trigger armature such that they are ineffectiveas they pass the magneto core 128. If the spacing of the legs and polesof trigger armature and core is improper, the armature will appear tothe magneto core 128 as the magneto armature and produce a maverickspark.

The foregoing embodiments have brought several important features incommon which constitute important novel aspects of the instantinvention. These include the use of trigger windings, the use of meansto initiate and terminate conduction through a solid state controldevice, the provision of means to prevent the generation of undesirableor maverick spark impulses, the use of threshold devices for augmentedpower capabilities and improved spark characteristics, and the provisionof means to provide a step function of flux change in the magneto coilsto produce a voltage impulse of improved shape and sufiicient toinitiate spark ignition. Moreover, the instant disclosure provides meansfor controlling timing, either on a preset or adjustable basis or inresponse to engine speed. Furthermore, utilizing the teaching of theinstant invention, one may provide augmented flux change in th magnetocoils by virtue of rapid switching and energy storage for switchingpurposes. Various other constructions and variations will immediatelyappear to one skilled in the art which will utilize all of the foregoingteaching.

Without further elaboration, the foregoing will so fully explain thecharacter of the invention that others may, by applying currentkonweldge, readily adapt the same for use under varying conditions ofservice, while retaining certain features which may properly be said toconstitute the essential items of novelty involved, which items areintended to be defined and secured by the following claims.

What is claimed is:

1. In a magneto system including stator means, rotor means cyclicallymovable relative to said stator means and a magnetoelectric assemblyincluding armature means on said rotor means and magnetically coupledfirst and second winding means on said stator means, said armature meansinducing voltages in said first and second winding means as said rotormeans moves relative to said stator means, the improvement comprising asolid state threshold device having conductive terminals connectedacross said first winding means and trigger coil means mounted on saidstator means and providing a timed bipolar cyclic electrical signal inresponse to movement of said rotor means, said trigger coil means beingelectrically connected to said threshold device to render said thresholddevice conductive at an initial time in the cycle of movement when saidsignal is of one polarity and substantially nonconductive at apredetermined later time during said cycle of said rotor when saidpolarity is reversed, said solid state threshold device havingcharacteristics such that it remains nonconductive until said triggercoil means renders it conductive in a subsequent cycle, a high voltageimpulse being generated in said second winding means in response to saidtimed electrical signal.

2. The magneto system of claim 1 including a trigger coil assemblymounted on said stator means, a source of magnetic flux mounted on saidrotor means, magnetic pole pieces mounted on said rotor in associationwith said flux source, said pole pieces cooperating with said magnetocoil assembly to generate a voltage therein, and second pole piecesmounted in said rotor in association with said flux source, said secondpole pieces cooperating with said trigger coil assembly to generate avoltage therein, and circuit means operatively interconnecting said coilassemblies.

3. The magneto system of claim 1 wherein said trigger coil meansprovides timed electrical signals having a gradually increasingmagnitude directly related to the rate of movement of said rotor means,conduction between said conductive terminals being terminated at earliertimes in said cycle for increased rates of rotor movement.

4. The magneto system of claim 1 wherein said trigger coil meanscomprises a first trigger coil and a second trigger coil, each providinga bipolar cyclic signal to said threshold device, said threshold devicebeing rendered nonconductive at low rates of rotor movement in responseto the combined energy of said coils, the signal of one of said coilsterminating conduction through said threshold device at an advanced timein said cycle for increased rates of rotor movement 5. The magnetosystem of claim 4 wherein the effective ratio of inductance toresistance in said first coil is substantially different from theeffective ratio of inductance to resistance in said second coil.

6. The magneto system of claim 5 including means for altering theefiective ratio of inductive reactance to resistance of one of saidcoils, the relationship of the time at which the threshold device isrendered nonconductive to the rate of rotor movement being controllablethereby.

7. The magneto system of claim 1 wherein said trigger coil meansincludes a first coil connected to said threshold device to initiateconduction therein at said initial time, a second coil and an energystorage circuit energized therefrom, and a third coil connected to saidenergy storage circuit to apply said energy storage circuit to saidthreshold device at said later time.

8. In a magneto system including stator means, rotor means cyclicallymovable relative to said stator means and a magnetoelectric assemblyincluding two poled armature means and a flux source on said rotormeans, an E-shaped magnetic core having first, center and last legs andsecured to said stator means, said core cooperating with said armaturemeans to provide low reluctance flux paths first between said first andcenter legs and subsequently between said center and last legs as saidrotor moves throughits cycle, and first and second winding means coupledto said center leg to produce in each of said winding means a firstvoltage, a second voltage of reversed polarity and a third voltage ofthe same polarity as said first voltage as said rotor moves through saidcycle, the improvement comprising a solid state threshold device havingconductive terminals connected across said first winding and poled forconduction in response to said second voltage and trigger coil meansmounted on said stator means and providing a timed cyclic bipolarelectrical signal in response to movement of said rotor means, saidtrigger coil means being electrically connected to said threshold deviceto render said threshold device conduc tive at an initial time in thecycle of movement when said signal is of a first polarity andsubstantially nonconductive at a predetermined later time during saidcycle of said rotor when said polarity is reversed, said solid statethreshold device having characteristics such that it remainsnonconductive until said trigger coil means renders it conductive in asubsequent cycle, a high voltage impulse being generated in said secondwinding in response to said timed electrical signal.

9. The magneto system of claim 8 wherein said trigger coil meanscomprises a first trigger coil and a second trigger coil, each providinga bipolar cyclic signal to said threshold device, said threshold devicebeing rendered nonconductive at low rates of rotor movement in responseto the combined energy of said coils, the signal of one of said coilspredominating in terminating conduction through said threshold devicefor increased rates of rotor movement.

10. The magneto system of claim 9 wherein the eifective ratio ofinductance to resistance in said first coil is substantially ditferentfrom the efiective ratio of inductance to resistance in said secondcoil.

11. The magneto system of claim 10 including means for altering theeifective ratio of inductance to resistance of one of said coils, therelationship of said high voltage impulse to rate of rotor movementbeing controllable thereby.

12. The magneto system of claim 8 wherein said trigger coil meansincludes a first coil connected to said threshold device to initiateconduction therein at said initial time, a second coil and an energystorage circuit energized therefrom, and a third coil connected to saidenergy storage circuit to apply said energy storage circuit to saidthreshold device at said later time.

13. In a magneto system including a magnetoelectric assembly havingwinding means and flux means, said winding means and flux means beingcyclically movable relative to one another in a flux linkingrelationship, the improvement comprising a solid state threshold devicehaving conductive terminals connected across said winding means and acontrol terminal, and means activated by 13 said cyclic movement andelectrically connected to the control terminal of said threshold deviceto render said threshold device conductive at an initial time in thecycle of movement and substantially nonconductive at a laterpredetermined time during said cycle, said solid state threshold devicehaving characteristics such that it remains nonconductive until saidmeans activated by said cyclic movement renders it conductive in a subsequent cycle, a high voltage impulse being generated in said Windingmeans in response to the rendering of said threshold devicenonconductive.

14. In a magneto system including a magnetoelectric assembly havingmagnetically coupled first and second winding means and flux means, saidwinding means and flux means being cyclically movable relative to oneanother in a flux linking relationship, the improvement comprising asolid state threshold devicehaving conductive terminals connected acrosssaid first Winding means and a control terminal and control meansactivated by said cyclic movement and electrically connected to saidcontrol terminal to render said threshold device conductive at aninitial time in the cycle of movement and substantially nonconductive ata later predetermined time during said cycle, said solid state thresholddevice having characteristics such that it remains nonconductive untilsaid means activated by said cyclic movement renders it conductive in asubsequent cycle, a high voltage impulse being generated in said secondwinding means in response to the rendering of said threshold devicenonconductive.

15. The magneto system of claim 14 wherein said threshold device has ananode connected to one terminal of said first winding means and acathode connected to the other terminal of said first winding means, andwherein diode means is connected across said first winding with itscathode connected to said one terminal and its anode connected to saidother terminal.

References Cited UNITED STATES PATENTS 2,583,466 1/1952 Brownlee 310-1533,051,870 8/1962 Kirk 315177 3,186,397 6/1965 Loudon. 3,229,162 1/ 1966Loudon 315218 X 3,253,164 5/1966 Konopa. 3,312,860 4/ 1967 Sturm.

ORIS L. RADER, Primary Examiner.

H. HUBERFELD, Assistant Examiner.

